/*
 * Copyright (C) 2006-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */

package org.alfresco.jlan.server.filesys.loader;

import java.util.LinkedList;

/**
 * File Request Queue Class
 *
 * <p>Synchronized queue of FileRequest objects.
 *
 * @author gkspencer
 */
public class FileRequestQueue {

	//	List of file requests

	private LinkedList<FileRequest> m_queue;

	/**
	 * Class constructor
	 */
	public FileRequestQueue() {
		m_queue = new LinkedList<FileRequest>();
	}

	/**
	 * Return the number of requests in the queue
	 *
	 * @return int
	 */
	public final synchronized int numberOfRequests() {
		return m_queue.size();
	}

	/**
	 * Add a request to the queue
	 *
	 * @param req FileRequest
	 */
	public final synchronized void addRequest(FileRequest req) {

		//	Add the request to the queue

		m_queue.add(req);

		//	Notify workers that there is a request to process

		notifyAll();
	}

	/**
	 * Remove a request from the head of the queue
	 *
	 * @return FileRequest
	 * @exception InterruptedException
	 */
	public final synchronized FileRequest removeRequest()
		throws InterruptedException {

		//	Wait until there is a request

		waitWhileEmpty();

		//	Get the request from the head of the queue

		return m_queue.removeFirst();
	}

	/**
	 * Remove a request from the head of the queue without waiting
	 *
	 * @return FileRequest
	 */
	public final synchronized FileRequest removeRequestNoWait() {

		//	Get the request from the head of the queue

		return m_queue.removeFirst();
	}

	/**
	 * Remove all requests from the queue
	 */
	public final void removeAllRequests() {
	  m_queue.clear();
	}

	/**
	 * Wait for a file request to be added to the queue
	 *
	 * @exception InterruptedException
	 */
	public final synchronized void waitWhileEmpty()
		throws InterruptedException {

		//	Wait until some work arrives on the queue

		while ( m_queue.size() == 0)
			wait();
	}

	/**
	 * Wait for the file request queue to be emptied
	 *
	 * @exception InterruptedException
	 */
	public final synchronized void waitUntilEmpty()
		throws InterruptedException {

		//	Wait until the request queue is empty

		while ( m_queue.size() != 0)
			wait();
	}
}
